Engine knock is a behavior wherein the normally controlled burn activity of an internal combustion engine is perturbed by premature ignition of the fuel/air mixture. There are many causes of knock, and it is very important to eliminate the possibility of excessive knock of any type so as to prevent serious damage to an engine, and loss of significant engine power and operating efficiency.
Despite advances heretofore in the science of addressing the issue of engine knock issue, the “gold standard” for real-time knock detection involves the bolting of a copper tube to the block of an engine for the purpose of permitting a trained technician to listen, via the tube, for audible sounds believed to be interpretable as knock. This very subjective and error-prone method is, of course, often quite unacceptable, and accordingly, there have been many efforts in recent years directed toward developing more sophisticated techniques for assessing internal combustion engine knock.
Recognizing that there have been many “science side” (rather then “art side”) proposals and advancements for detecting and analyzing engine knock, the engine-knock analysis system disclosed herein employing the features—dynamic noise-reduction baselining features—of the present invention nevertheless offers a significant and unique advance in the ability to accomplish precision, noise-suppressed analyzable knock detection, and to do so very rapidly, very accurately, and on-the-fly, so-to-speak, during real-time engine operation.
In a manner of thinking about the practice proposed by the present invention, that practice is based upon having access, effectively, to a body of carefully engine-noise-reduced, frequency-domain-spectral, engine-operating, energy-content data derived from an operating engine—data of a kind which is expected to contain, in one or more experientially pre-selected, knock-related frequency bands (referred to herein as spectral bins), evidence of any engine-knock behavior. Such access, enhanced by the methodology of the present invention, leads toward the step of comparing, ultimately, and via a predecessor practice referred to as bin-summing, the sum total of noise-reduced spectral energy reflected in those selected spectral bins with a pre-determined, user-chosen spectral energy threshold value deemed to be indicative of transition of an engine cylinder into a confirmable engine-knock behavior condition. The finding of a noise-reduced spectral energy value which exceeds this spectral energy threshold produces herein a positive declaration of the presence of engine knock. The practice of bin-summing, discussed very summarily later herein, which is not, per se, any part of the present invention, is described fully in a predecessor, companion, background U.S. Patent which is U.S. Pat. No. 7,181,339 B2, issued Feb. 20, 2007, for “Real-Time Spectral Analysis of Internal Combustion Engine Knock”. The full disclosure content of that patent is hereby incorporated herein by reference.
This currently presented system, which employs the present invention as disclosed herein, is an enhanced version of the predecessor system described in the '339 patent, and specifically a version which is significantly enhanced in relation to a real-time manner of developing important noise-reduction baseline data.
In the mentioned predecessor system, a method and a system are described for gathering data from an operating internal combustion engine enabling the easy and accurate determination of engine-knock behavior. The present invention, as was just above stated, involves an improvement in the real-time practice of that prior-disclosed system—an improvement in the sense of a hereinbelow described, new and unique practice (referred to as dynamic baselining) for acquiring dynamic, noise-reduction baseline data to be used in the determination of a baseline noise-reduction index value which can then be employed to remove knock-information-obscuring engine noise from relevant, acquired engine-operating data so as better to detect, and clearly identify and analyze, an engine-knock condition.
In accordance with this prior-existing (predecessor) system disclosure, baseline noise-reduction data is derived in a pre-engine-testing-condition mode of operation, wherein an engine that is to be tested for engine-knock behavior is specifically operated initially in a non-normal operating mode wherein, with a very high degree of certainty, no engine-knock condition will exhibit. It is clear from the description given regarding this prior-disclosed system and practice that baseline, or baselining, data is acquired under circumstances which are created before an engine is put into a real-time test mode for the purpose of detecting engine knock.
There are many circumstances, however, including circumstances involving engines that have relatively short operating lifetimes between required maintenance activities, with respect to which it is important, if possible, not to use up valuable engine operating time in such a pre-operation mode, simply for the purpose of detecting baseline noise data (i.e., baseline noise-reduction data). Put another way, the present invention recognizes the importance of avoiding “eating into” an engine-operating lifecycle between maintenance events by uniquely utilizing a baseline data-collection technique which can function during what is otherwise normal engine operation.
Fundamentally, and in accordance with practice of the present invention, and during a full test procedure (i.e., not within a pre-test situation), referred to herein as a test span, cylinder pressure data is employed (preferably) to identify, during pre-compression and pre-ignition cyclic periods associated with a selected, monitored cylinder, a crank-angle window wherein an operating engine will most likely operate in a behavior-region wherein any engine noise detected will most confidently be non-knock engine noise.
As a momentary informational aside at this point, a test-span begins with initial engine operation, and ends when a knock event is detected in the behavior of a cylinder.
In accordance with the invention, and with respect to observations made of internal, operating-engine cylinder pressure under these full-test conditions, a baseline, or baselining, window is defined—an action referred to also as windowing, as window-defining, as window identification, and as crank-angle windowing—with beginning and ending crank angles in relation to a suitably discerned peak cylinder pressure value. This window is deemed to be a window during which no engine knock behavior is expected. As will be seen, this baselining window immediately precedes a linked crank-angle range selected for monitoring because of the high likelihood of detecting evidence of cylinder knock behavior during that linked range. The scope or extent of this linked crank-angle range is predetermined on the basis of expert knowledge about the expected performance of an engine being tested. Collectively, the baseline window range and the so-called linked range are referred to herein as a crank-angle monitoring range.
Crank-angle window-defining for a monitored cylinder may be performed either (a) once-only, as during a first (or early) operating cycle within an engine test span, to be employed as the operative baselining window in relation to all subsequent operating cycles during that test span, or (b) independently during each operating cycle for employment only in relation to that cycle.
Thus, whereas in the prior practice described in the above-referenced, predecessor U.S. Patent, collection, or derivation, of baseline noise-reduction data takes place in a circumstance wherein an engine is forced entirely into a special, predictable non-knock condition in a pre-test-span operation, according to the present invention, such baseline data is obtained as a body during conditions of normal knock-possible engine operation by looking at selected crank-angle portions of cylinder operating cycles wherein knock is deemed to be unlikely to occur—i.e., in the determined crank-angle baselining window.
While there may be many different ways in which signal-processing selection—also referred to herein as calculation—of an appropriate window for the collection of baseline data may be performed, two which have been found to be very useful include: (a) a practice (Mode I) wherein high-frequency filtering is applied to acquire, relative to crank-angle status, cylinder-pressure data to detect steep angles of pressure change (leading to sharp pressure peaks) so as to indicate the onset of an event which should not be included in baseline data; and (b) a practice (Mode II) wherein an initial window is suitably established (as by implementation once of the Mode I practice just described), and thereafter cylinder peak pressures are monitored from cycle-to-cycle to determine whether or not there are any significant jumps in the crank-angle positions of steep-angle cylinder-pressure changes which indicate the possible need to change, and/or shift, the crank-angle baselining window boundaries. In both approaches, which relate to certain peak-pressure information, a baselining window is established to reside in a range of crank angles that precede a crank angle at which a sharp pressure rise is detected, and it is in this selected crank-angle window that baseline data is acquired during each cycle.
These two signal-processing windowing practices, in relation to their respective details of implementation as signal-processing modalities, are specifically and generally conventional in nature, are well understood by those skilled in the relevant art, do not form any part of the present invention, and therefore are not set forth in any greater detail herein.
Following such cylinder-specific baselining window identification (depending upon which of the two just-mentioned modes of windowing is employed), and thereafter during each engine full-test operating cycle, cylinder-specific data relating to engine noise is gathered during the relevant window, and is used, “on the fly”, to create baseline noise-reduction data which will be applied to later-in-the-associated-cycle, acquired data from which engine-knock behavior may be detected.
Thus, practice of the present invention involves a cycle-by-cycle determination of baseline data derived during such a window, with a particular baseline noise-reduction index value therefore developed for each cycle of operation, and with all of this being done during “full-bore” engine-operational testing in a test span.
Reiterating what has just been described, in accordance with the present invention, during the acquisition and ultimate use of such dynamically acquired baseline data, a subject engine operates in a full, normal mode of operation wherein knock may occur (or may be induced to occur). In each operating cycle of a cylinder selected for monitoring, and following the mentioned, windowed period of pre-compression time during which baseline noise-reduction data is acquired, as the selected engine cylinder advances directly into a combustion portion of its cycle, data continues to be acquired during the entire crank-angle monitoring range relating to cylinder pressure conditions, and is treated, cycle-by-cycle, with the just-detected baseline noise data to remove that noise data, and to expose any engine-knock behavior which has occurred during that cycle.
From what has just been generally outlined above regarding the baseline windowing and baseline-data noise-reduction employment practices of the present invention, it should be evident that there are up to two, different cooperative “levels”—single and dual—of dynamic baselining performance offered by the present invention. Single-level dynamic baselining involves single-stage, multiple-cycle-use, crank-angle windowing, with cycle-specific noise-reduction baselining data being derived from a fixed-boundaried baselining window, and then employed cycle-specifically within each and every relevant-cylinder operating cycle. Dual-level dynamic baselining adds to single-level baselining the practice of cycle-specific, plural-stage crank-angle windowing.
In the detailed description of the invention presented herein, and in order to place the invention in an appropriate operational context, the nature and features of the invention are described in the full setting of a representative engine-knock spectral analysis. Much of this descriptive setting is drawn from the text that is contained in the above-referred-to U.S. Patent, abbreviated where elaboration is not required specifically in the present text, with the suggestion given for the reader to consult the earlier text in that prior patent for a fuller exposition of subject matter not relevant to the understanding, per se, of the present invention.
Accordingly, the important features and advantages which are offered by the present invention will shortly become more fully apparent as the detailed description thereof which follows below is read in conjunction with the accompanying several drawings.